Molbiol 2011-04-metabolism
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Molbiol 2011-04-metabolism Molbiol 2011-04-metabolism Presentation Transcript

  • ЛЕКЦИЯ 3-2
    • Метаболизм
    • Metabolism: The sum of the chemical reactions in an organism
    • Catabolism: The energy-releasing processes
    • Anabolism: The energy-using processes
    Microbial Metabolism
  • Microbial Metabolism
    • Catabolism provides the building blocks and energy for anabolism.
    Figure 5.1
    • A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell.
    • Metabolic pathways are determined by enzymes.
    • Enzymes are encoded by genes.
    PLAY Animation: Metabolic Pathways (Overview)
    • The collision theory states that chemical reactions can occur when atoms, ions, and molecules collide.
    • Activation energy is needed to disrupt electronic configurations.
    • Reaction rate is the frequency of collisions with enough energy to bring about a reaction.
    • Reaction rate can be increased by enzymes or by increasing temperature or pressure.
  • Enzymes Figure 5.2
  • Enzymes
    • Biological catalysts
      • Specific for a chemical reaction; not used up in that reaction
    • Apoenzyme: Protein
    • Cofactor: Nonprotein component
      • Coenzyme: Organic cofactor
    • Holoenzyme: Apoenzyme plus cofactor
  • Enzymes Figure 5.3
  • Important Coenzymes
    • NAD +
    • NADP +
    • FAD
    • Coenzyme A
  • Enzymes
    • The turnover number is generally 1-10,000 molecules per second.
    PLAY Animation: Enzyme–Substrate Interactions Figure 5.4
  • Enzyme Classification
    • Oxidoreductase: Oxidation-reduction reactions
    • Transferase: Transfer functional groups
    • Hydrolase: Hydrolysis
    • Lyase: Removal of atoms without hydrolysis
    • Isomerase: Rearrangement of atoms
    • Ligase: Joining of molecules, uses ATP
  • Factors Influencing Enzyme Activity
    • Enzymes can be denatured by temperature and pH
    Figure 5.6
  • Factors Influencing Enzyme Activity
    • Temperature
    Figure 5.5a
  • Factors Influencing Enzyme Activity
    • pH
    Figure 5.5b
  • Factors Influencing Enzyme Activity
    • Substrate concentration
    Figure 5.5c
  • Factors Influencing Enzyme Activity
    • Competitive inhibition
    Figure 5.7a–b
  • Factors Influencing Enzyme Activity
  • Factors Influencing Enzyme Activity
    • Noncompetitive inhibition
    Figure 5.7a, c
  • Factors Influencing Enzyme Activity
    • Feedback inhibition
    Figure 5.8
  • Ribozymes
    • RNA that cuts and splices RNA
  • Oxidation-Reduction
    • Oxidation is the removal of electrons.
    • Reduction is the gain of electrons.
    • Redox reaction is an oxidation reaction paired with a reduction reaction.
    Figure 5.9
  • Oxidation-Reduction
    • In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations.
    Figure 5.10
  • The Generation of ATP
    • ATP is generated by the phosphorylation of ADP.
  • The Generation of ATP
    • Substrate-level phosphorylation is the transfer of a high-energy PO 4 – to ADP.
  • The Generation of ATP
    • Energy released from the transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP by chemiosmosis.
  • The Generation of ATP
    • Light causes chlorophyll to give up electrons. Energy released from the transfer of electrons (oxidation) of chlorophyll through a system of carrier molecules is used to generate ATP.
  • Metabolic Pathways
  • Carbohydrate Catabolism
    • The breakdown of carbohydrates to release energy
      • Glycolysis
      • Krebs cycle
      • Electron transport chain
  • Glycolysis
    • The oxidation of glucose to pyruvic acid produces ATP and NADH.
    Figure 5.11, step 1
  • Preparatory Stage
    • Two ATPs are used
    • Glucose is split to form two Glucose-3-phosphate
    1 3 4 5 Figure 5.12, step 1
  • Energy-Conserving Stage
    • Two Glucose-3-phosphate oxidized to two Pyruvic acid
    • Four ATP produced
    • Two NADH produced
    9 Figure 5.12, step 2
  • Glycolysis
    • Glucose + 2 ATP + 2 ADP + 2 PO 4 – + 2 NAD +  2 pyruvic acid + 4 ATP + 2 NADH + 2H +
    PLAY Animation: Glycolysis
  • Alternatives to Glycolysis
    • Pentose phosphate pathway
      • Uses pentoses and NADPH
      • Operates with glycolysis
    • Entner-Doudoroff pathway
      • Produces NADPH and ATP
      • Does not involve glycolysis
      • Pseudomonas, Rhizobium, Agrobacterium
  • Cellular Respiration
    • Oxidation of molecules liberates electrons for an electron transport chain.
    • ATP is generated by oxidative phosphorylation.
  • Intermediate Step
    • Pyruvic acid (from glycolysis) is oxidized and decarboyxlated.
    Figure 5.13 (1 of 2)
  • Krebs Cycle
    • Oxidation of acetyl CoA produces NADH and FADH 2 .
    PLAY Animation: Krebs Cycle
  • Krebs Cycle Figure 5.13 (2 of 2)
  • The Electron Transport Chain
    • A series of carrier molecules that are, in turn, oxidized and reduced as electrons are passed down the chain.
    • Energy released can be used to produce ATP by chemiosmosis.
    PLAY Animation: Electron Transport Chains and Chemiosmosis
  • Figure 5.11
  • Chemiosmosis Figure 5.16
  • Chemiosmosis Figure 5.15
  • Respiration
    • Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O 2 ).
    • Anaerobic respiration: The final electron acceptor in the electron transport chain is not O 2 . Yields less energy than aerobic respiration because only part of the Krebs cycles operations under anaerobic conditions.
  • Anaerobic Respiration CH 4 + H 2 O CO 3 2 – H 2 S + H 2 O SO 4 – NO 2 – , N 2 + H 2 O NO 3 – Products Electron acceptor
  • Plasma membrane Mitochondrial inner membrane ETC Cytoplasm Cytoplasm Cytoplasm Prokaryote Mitochondrial matrix Krebs cycle Cytoplasm Intermediate step Cytoplasm Glycolysis Eukaryote Pathway
    • Energy produced from complete oxidation of one glucose using aerobic respiration.
    2 2 0 FADH 2 produced 10 4 Total 6 2 2 NADH produced 2 Krebs cycle 0 Intermediate step 2 Glycolysis ATP produced Pathway
    • ATP produced from complete oxidation of one glucose using aerobic respiration.
    • 36 ATPs are produced in eukaryotes.
    4 30 4 Total 4 0 From FADH 18 2 Krebs cycle 6 6 From NADH By oxidative phosphorylation 0 Intermediate step 2 Glycolysis By substrate-level phosphorylation Pathway